The invention is based on a hinge for connecting three levers [as generically defined by the preamble to claim 1].
Motor vehicle wiper systems have a wiper motor as their drive mechanism, along with a gear mechanism mounted on it whose drive shaft as a rule via a crank and articulated rods drives a crank that is solidly connected to a drive shaft for each windshield wiper.
In conventional wiper systems, a crank is solidly mounted on the drive shaft of the gear mechanism and on its other end has at least one power takeoff mechanism. This power takeoff mechanism forms a hinge, which connects a plurality of levers of a lever mechanism to one another.
From European Patent Disclosure EP 0 683 739 B1, a hinge is known that has a crank secured to a bearing bolt, forming a mechanical unit. The bearing bolt protrudes with its shaft through the crank, while in its end region remote from the crank it changes over into a spherical bolt head. The bolt head is supported at a first bearing ring, which is connected to a first drive rod. The inner bearing face of the first bearing ring is curved to correspond to the spherical surface of the bolt head, on the one hand to allow a pivoting motion of the first drive rod relative to the bolt head and on the other to secure against axial forces. The first bearing ring furthermore has a spherical outer face, which acts as a bearing face for a second bearing ring. This second bearing ring completely surrounds the first bearing ring and is inseparably connected to a second drive rod by casting. The bearing faces facing one another of the bearing rings are rounded in concave and convex form, respectively, and are oriented concentrically to the center point of the bolt head. They thus make possible an at least limited pivoting motion of the drive rods and the crank relative to one another. The two drive rods and the crank engage the bearing elements at various-sized spacings, so that the hinge and the drive rods and the crank are loaded in the region of the hinge by considerable bending moments. Furthermore, the hinge is relatively high in structure. To make it possible for the drive rods of the lever mechanism to be disposed substantially in the same plane, they and possibly the crank must be severely offset-bent.
Exemplary embodiments are also known in which the relationships between the crank and the drive rods are transposed. In all the versions, the drive rods and the crank are connected in three planes with the bearing parts, making for a tall hinge.
According to the invention, the hinge for connecting three levers of a lever mechanism comprises a first bearing shell to which a first lever is secured. The first bearing shell has an inner face, which acts as a bearing face for a second bearing shell. The second bearing shell comprises two sectors, which are each solidly connected to one lever. The sectors have outer faces through which they are supported and centered in the first bearing shell. Toward the inside, they are braced against one another by suitable bearing means, such as a knife-edge bearing.
Expediently, the bearing shells have spherical bearing faces, so that the levers are at least limitedly pivotable to all sides about the center point of the sphere. In a further feature of the invention, the sectors of the second bearing shell can furthermore have a concentric spherical dome, into which a securing ball is pressed, on which the sectors are braced against one another, so that the levers connected to them are pivotable not only relative to the third lever but also relative to one another in an arbitrary direction. The three levers are centered relative to one another only by the outer faces of the sectors of the second bearing shells and the inner face of the first bearing shell, so that because there are only a few fits, close tolerances among the parts can be adhered to.
The lever connected to the first bearing shell extends in a middle cross-sectional plane of the bearing shells, while the other two levers are located in the same plane, which has a slight spacing from the first lever. This spacing is determined only by the height of the sectors and the height of the levers. The hinge is therefore extremely shallow and is loaded only by slight bending moments. In a feature of the invention, the levers of the hinge are made from sheet metal, and the second and third levers in part have a U-shaped profile. The U-shaped profile lends greater torsional and bending strengths to the levers and requires less use of materials in comparison to solid profiles. The bearing shells comprise plastic and are injection molded onto the associated levers, creating a solid, positive connection. The selected profile of the levers and the materially bonded and optionally positive connected to the bearing shells bring about a favorable transmission of force.
In a further variant of the invention, the hinge comprises a bearing shell to which a first lever is secured. The bearing shell has a spherical inner face, which acts as a bearing face for two sectors that are formed onto the associated levers. The sectors have spherical outer faces and spherical inner faces, which in turn embrace a ball. The bearing shell is expediently of plastic and is injection molded onto the associated lever. In this variant, the second bearing shell is formed in a simple way by the sectors, which are formed directly onto the sheet-metal levers. Further advantages will become apparent from the ensuing description of the drawing.